Exploring for oil and gas takes a lot of money
and know how to pull off as it requires first a comprehensive understanding of
the fundamentals of
petroleum Geology.
Oil and gas are, after all, essential petroleum resources that are found deep
within the earth’s crust, although there are cases where they may be found on
the surface as well, but not in abundant commercial quantities.

Liquid oil and liquid natural gas underneath are
found in porous and permeable rocks (also called reservoirs) that have
collected these precious materials for thousands of years. There are four
essential types of geologic features that contain oil and gas deposits, namely:

* Oil and gas source rocks

* Reservoir rocks

* Seals

* Traps

The figure below shows how the four features can
contain oil and gas in a configuration that allows explorers to tap each part
separately.

Figure 1. Arrangement of oil and gas source
rocks, a reservoir, a seal, and a trap in a way that has allowed the natural
accumulation of oil and gas.

Oil and
Gas Source Rocks

Oil and gas can be found in sedimentary
source-rocks that were deposited in very quiet water, such as stagnant swamps,
shallow calm marine bays, or in ancient deep underwater basins. Source rocks
are made up of extremely minute mineral components. Within the spaces between
these mineral fragments are contained the remains of organic substances, such
as wood bits, algae, or pieces of soft plant materials. Once these tiny
sediments are gradually overlain through continuous sedimentation, heat and
pressure increase, turning these soft organic sediments into solid rock strata.
With further accumulation of sediments and subsequent increase of temperatures
above 120o C (250o F), the organic deposits start to be
"cooked", producing oil and natural gas which are then removed from
the source-rock strata.

It takes thousands of years for this process to
take place before commercial volumes of what is called thermogenic (that is,
produced by heat) oil and gas can accumulate. Organic materials mostly made up
of wood fragments in source rocks will produce natural gas upon maturation
while algae or the soft parts of plants on land will produce both oil and
natural gas.

At temperatures above 150o C (300o
F), organic remains would have generated most of the oil they can produce. The
remaining oil in the source rock or any oil that has been trapped in adjacent
reservoirs will be converted into natural gas.

Natural gas can also be produced in certain
organic-rich sedimentary rocks through bacterial processes in shallow burial
depth prior to thermal maturation temperatures are attained. This process
called biogenic-gas (that is, produced by organisms) generation occurs at
depths of less than 2,000 ft and produces less amounts of gas compared to thermogenic
gas.

Oil and
Gas Reservoir Rocks

Oil and gas reservoir rocks have high porosity
and are also highly permeable, thus, allowing oil and gas that have been
expelled from source rocks to enter or seep into adjacent reservoir rocks.
Sandstones, limestones and dolomites comprise most oil and gas reservoir rocks.

Seals

Oil and gas that have occupied the air spaces
within reservoir rocks freely move about to seek other spaces or less dense
environments. Since most reservoir rocks are originally saturated with saline
groundwater and since saline ground water is denser than oil and gas, the
latter rises upward through the water-saturated pore spaces until they meet a
barrier of impermeable rock or what is called a seal. Seals are usually very
fine-grained rocks, such as shale, with no pore spaces or are impermeable to
fluids.

Oil and
Gas Traps

As oil and gas migrate up and within reservoir
rocks, they eventually encounter barriers that block their way according to the
configuration of the reservoir rock and the presence of one or more seals. This
arrangement produces a trap. A trap can be either structural or stratigraphic.
Structural traps are created when the reservoir rock and the seal caver have
been deformed by folding or faulting of rock layers through geologic eras
(Figure 2).

Figure 2. Folded strata that form a structural
trap.

Stratigraphic traps are created when the
reservoir rock is deposited as a discontinuous layer. Seals are deposited
beside and on top of the reservoir. A typical case of this form of trap is a
coastal barrier island. Impermeable shale seals are deposited both landward and
seaward of the barrier island, which forms an elongate lens of sandstone. What
forms is a porous sandstone reservoir within shale seals which may in turn be
source rocks.

Figure 3. A discontinuous layer of sandstone
that forms a stratigraphic trap.

The primary question now is where such oil and
gas deposits can be found exactly in any given region and how to extract them
at a commercially viable cost. This is the job for a company such as Trinity
Energy Group. Trinity Energy Group has many years of experience in oil and gas
exploration, drilling, production and management of operations in North
America, Central America and all over the world. It can provide you with the
next big step toward achieving your own investment goals.